The present invention relates to extensible, scraping guards used especially to protect machine slideways and in particular to an apparatus on which the scrapers are mounted and to a related construction method.
In the mechanical engineering sector, a common problem connected with the use of certain types of chipforming machine tools and certain types of manipulators and mobile robotized systems is how to protect some of the moving parts against damage due to the combined action of chippings, dust and lubricating coolants from the cutting areas.
To protect against damage of this kind, machines are usually fitted with scraping guards consisting basically of a metal casing that is connected to a moving part of the machine and that has an oil scraper made of an elastically yielding material (for example, polyurethane). The oil scraper projects from the casing against the adjacent fixed part of the machine, for example, a slideway and scrapes it as the machine moves. In this way, it fills the space in the slideway in which the machine runs, preventing dirt from getting into it, and as it moves, also removes foreign matter from the surface of the slideway.
Scraping guards of this kind, called simply scrapers by experts in the trade, are usually applied to the moving part of the machine and are shaped to match the shape of the slideway on which the movable part of the machine runs, with an outer edge that fits the slideway exactly so as to keep the surface of the slideway clean not only by scraping off any dirt deposits but also by preventing chippings and other foreign matter from making their way into the slideway.
An apparatus of this kind, corresponding substantially to the preamble to claim 1, and described also in patent publication U.S. Pat. No. 4,254,531, comprises a frame which holds the scrapers and which consists of a plurality of single lengths of section fitted together in pairs where the two lengths meet at one corner, and connecting squares having first contact faces which lie flat against opposing perimetric faces of the lengths of section, these lengths of section having a longitudinal groove in which the scrapers are retained and from which they extend outwards towards a metal case adjacent to the case that mounts the apparatus.
The main advantage of using connecting squares to connect up the parts of the scraper is that they allow frames with complex shapes to be made to match the shapes of different types of slideways, including L-, Z- and Omega-shaped slideways.
However, in the known solution, the lengths of section are made from extruded aluminum alloy and, in order to confer sufficient stiffness on the frame as a whole but without unduly increasing the contact pressure between the squares and the perimetric faces of the sections, the squares used have large surfaces with rather long, cumbersome arms. Moreover, the lengths of section are shaped in such a way as to present internal cavities in which the squares are press fitted and the fit then reinforced by punching and or spot welding.
Finally, to securely attach the scrapers to each other at the join between two contiguous sections, some additional, separate connecting elements, housed inside the scrapers themselves, are used.
In another solution known to experts in the trade, the mounting frames are made by welding the lengths of section directly to each other without using connecting squares. This solution is especially designed to confer adequate rigidity and strength on the structural connections, especially when the frame is made from lengths of steel section. However, the disadvantage of this solution is that, especially in the case of frames with complex shapes, welding the parts together produces thermal expansion and causes considerable deformation. As a result, once the frame has been welded, a lengthy and complex straightening operation is inevitably required to confer a degree of precision to match the precision typical of the shape of the slideways that the guards are used on. This considerably increases the cost of the finished product.
The aim of the present invention is to overcome the above mentioned disadvantages and to combine flexibility, as can be attained with the connecting squares, with the strength and rigidity of welded steel constructions while at the same time avoiding the drawbacks due to the constructional complexity and thermal expansion typical of the two main types of conventional solutions described above.